Drawing metal



Patented Jan. 12, 1937 UNETEE STATES mews PATENT QFFEQE No Drawing.Application December 28, 1935,

Serial No. 56.535

8 Claims.

This invention relates to the cold working of metals, and moreparticularly to cold drawing tubes and other sections, to which theinvention is especially applicable and for which reason it will bedescribed with special reference thereto.

alloy steels normally dificult to draw; and which possesses otheradvantages which will appear hereinafter.

Another objectis to provide a lubricant for use in cold working metals,particularly cold drawing ferrous metal tubing, which is easily anpliedto the stock and is easily removed after the working operations havebeen finished; which is cheap; and which is particularly adapted for thepractice of the method embodied in the inven tion.

Having reference'particularly to cold drawing operations, in thepractice of which the invention is especially beneficial, it iscustomary to use a lubricant to assist the drawing and in an attempt tominimize the formation of surface'de-- fects. customarily the drawingstock, such for example as tubing, is annealed and pickled,.followingwhich a lubricant is applied to the inside and outside surfaces and thetube is drawn through a die and over a mandrel to reduce the diameterand wall thickness, with reduction in cross sectional area.

Tallow materials, such as tallow, emulsions, are used commonly tolubricate ordinary steels. Various other lubricants are used or havebeen proposed, particularly for alloy steels of certain types. Forinstance, special oils are used in particular cases, and some types ofsolid lubricants have been: proposed. None of these prior lubricants iswholly satisfactory from all standpoints or for general use. Thus, thetallow lubricants are satisfactory for some steels or some purposes, butthey are not generally applicable to all steels with completelysatisfactory results. For example, tallow lubricants are unsuited forthe.production of small diameter thin-walled tubes which when drawn withsuch a lubricant must be annealed, pickled and relubricated after eachpass, 55 they are not suitable for drawing stainless which is applicableto stainless steel and other steel tubing. Where oils are used it iscommon practice to burn off the residual oil; this is objectionablebecause fumes of obnoxious character or detrimental to health may beformed, thus necessitating the installation of ventilating apparatus.

Particularly serious difiiculties are encountered in the drawing'ofalloy steels, especially the socalled stainless steels, in the drawingof which with previously used lubricants seizure occurs between the tubeand the dies and mandrels. This is objectionable because such seizurecauses surface defects which are objectionable from the standpoint ofappearance and may render the product not acceptable to the purchaser,or because of damage to the tools. To overcome this a practice has beento lead-dip the tubing prior to drawing but such a practice is notdesirable because the use of the lead bath increases the drawing costs,which are further increased through the necessity and difficulty ofremoving residual lead when the drawing has been completed.

I have discovered, and it is upon this that my invention is predicated,that a dry coating of a mixture of lamp black'and a suitable adhesivesatisfactorily prevents seizing, gives improved lubrication as comparedwith other lubricating materials known to me, and at least with ordinarysteels makes it possible to draw them to any size that the strength ofthe steel in the point will stand, without scratching or pick-up on thetools. These and other advantages have been amply demonstrated both byextensive experimental workand by large scale commercial operations.

In accordance with the present invention, therefore, the diflicultiesoutlined hereinabove are overcome or minimized by the use of a lubricant comprising lamp black and an adhesive. In the practice of theinvention, a mixture of lamp black and adhesive, most suitably a liquidadhesive, is applied to the article to be worked, for instance a tube,the coating is dried, and the thus-coated article is then drawn incustomary manner. The adhesive element of the lubricant used in myinvention acts apparently to hold the lamp black particles in positionuntil they have entered the die, thus retaining all or substantially allof the lubricating material in position to af- 5o ford maximumlubricating eflect.

Various adhesives may be used in the practice of this invention. I nowprefer to use silicate solutions, especially aqueous sodium silicatesolutions. These possess the advantages that they 5| performsatisfactorily, are cheap, and present no fire hazard because of thelack of flammability of both the silicate and the solvent. and importantadvantage is that residues remaining after drawing can be removedquickly and cheaply.

The proportions of the lamp black and adhesive will vary according tothe steel and the severity of the drawing, and also according to thead.- hesive used. Stated generally, there must be enough lamp black tosatisfactorily lubricate, and enough adhesive to hold it in place. Onelubricant which I have found to be satisfactory for many purposes iscomposed of 110 gallons of 50 B. sodium silicate (water glass) solution,150 pounds of lamp black, and water to bring the mixture to 330 gallons.In the use of this and other compositions embodied within the inventionthe tube or other article is treated with the composition to provide acontinuous coating over the surfaces which are to be exposed to theworking tools. This may be accomplished most readily by dipping the tubeor other article into a tank containing the mixture. The coating is thendried, either by permitting the solvent to evaporate, or by the use ofdrying ovens or the like, thus producing a solid continuous coating oflubricant over the treated portion. The tube is then drawn.

As indicating the benefits to be derived from the invention, thelubricant mixture just described was used in the drawing of an order oftubing formed from S. A. E. 4615 steel. This tubing after applicationand drying of the lubricant was given a double cold pass, with a totalof 45 per cent reduction in area, with no intermediate annealing. Notrouble was encountered in the drawing operations, the surface of thetubing was satisfactory, and the tools were not damaged.

The same composition has also been applied to other commercialoperations with entire success. For example, it was used in the drawingof an order of tubing made from steel containing about 28 per cent ofchromium, about 5 per cent of nickel, and about 1.5 per cent ofmolybdenum. Before drawing the tubing had an outside diameter of 1.72inch and a wall thickness of 0.135 inch. The tubing was coated with thecomposition described, and was drawn in two passes, the first reducingit to 1.5 inch outside diameter and a wall thickness of 0.127 inch, andthe second reducing it to 1.25 inch outside diameter and a wallthickness of 0.125 inch. The total reduction in area was 34 per cent. Noannealing or relubrieating was done between the passes, but no pickup orchattering occurred. The residue left on the tubing after drawing waswashed off in ordinary soda and acid tubs and the tubing was thenannealed, and subsequently pickled, no difficulty being encountered inpickling. It then presented a very clean surface inside and out.

This particular type of steel had been very hard to draw with priorlubricating practice, and it had been almost impossible to pickle it.Thus, tubes from the lot just referred to were lubricated by applicationof a special sulfurized drawing oil,

containing about 3 per cent of sulfur, which had been found byexperience to be the best lubricant for this steel, but as thuslubricated they could not be drawn. The tube is dipped in the oil, thenburned off in a furnace, and then redipped and drawn. After each pass itis annealed and put through the cycle again. The

drawing diificulties have been so severe that sometimes two burning-oisteps have been neces- A further sary in each cycle thus increasingdrawing costs and aggravating pickling troubles. The picklingdifficulties probably arise from the residue left on the tubing as aresult "of the burning-off step, the residue being baked into thesurface when the tube is annealed. That residue burnt into the tube notonly interferes with but is not removed by pickling, and this causestrouble in the succeeding pass. As previously drawn, i. e., prior to myinvention, it has been necessary to sandblast this tubing in order toobtain satisfactory final finishes.

Adhesives other than silicates may also be used, such as glue andvarnish, and other materials adapted to act as adhesives in theproduction of dry coatings containing lamp black. Likewise, solidsubstances in addition to lamp black may be added to the lubricants. Forinstance, I have found that lithopone may be used in addition to lampblack without detrimentally affecting the drawing characteristics orsurface finish. As exemplifying such compositions reference may be-madeto one that has been used for commercial drawing operations. 480 poundsof Armours bone glue, 100 pounds of lamp black, 900 pounds of lithopone,and water to bring it to approximately 500 gallons. To preserve thecomposition there may be added about 5 pounds of carbolic acid. In theuse of this lubricant it is desirable to dry the dipped tubes in a hotair drier to expedite drying the coating to sufficient film strength topermit drawing. With that solution there have been satisfactorily drawnover 90,000 feet of tubing weighing in excess of tons and comprisingtubes made from S. A. E. 2315, S. A. E. 3140 and S. A. E. 1045 steels,and the well-known 188 chrome-nickel stainless steel. Of this steel25,000 feet were made from S. A. E. 2315, being 1.125 inch outsidediameter and 0.188 inch wall thickness. This material was given ananneal at 2050 F., coated with the foregoing composition, dried, andthen drawn twice, without annealing or pickling, to finish, each passeffecting about 20 per cent reduction in area. The yield of salabletubing was exceptionally high on this order, and it was estimated thatthe tool life was at least treble that obtained with prior lubricants.There was no tool pick-up, and die and mandrel marks were not found inthe inspection of the finished tubing. Similar results were obtainedwith the remainder of the tubing referred to. In contrast, the sametubing when drawn in single passes with tallow caused large mandrelbreakage.

Likewise, tubes of common steels, such as S. A.

E. 1015 and 1020 and having an outside diameter.

of 2 inches and a wall thickness of 0.12 inch were drawn with the lampblack-glue-lithopone lubricant in two passes to 1.25 inch outsidediameter and 0.083 inch wall thickness, effecting a total of 57 per centreduction in area, without pickling, annealing or redoping betweenpasses.

It thus appears that the invention makes it possible to cut down on thenumber of pickling and annealing cycles now used, especially in thesmaller sizes where a large number of passes have been necessary.

In the use of these lubricants it is desirable to avoid the formation oftears or other accumulations of the lubricating mixture prior to orduring drying. Thus, using glue solutions, the mixture may tend toaccumulate, or form tears, unless the tube has been carefully drained,and this excess accumulation may tend to cause formation of slightdents. This difficulty is overcome,-

It comprised however, by using rather thin draining the tubes, forexample,-at an angle of about 45 aiter dipping. The ability to usesolutions thin enough to avoid tears is another advantage of thesilicate adhesive compositions.

My work has shown that in using the lubricant provided by this inventionit is unnecessary to use also a lubricating oil, at least for manypurbeen applied.

poses. I now prefer, however, to use such an oil after the coating hasbeen dried because it tends to improve thesuriace finish. However, therather expensive drawing compound oils are unnecessary, and cheapmaterials, such as fuel oil, afiord satisfactory results owing to theimproved lubrication aflforded by the invention.

My work has shown that the adhesive is necessary to obtain the fullbenefits of the invention.

For instance, suspensions of lamp black in drawing oil have been appliedto tubing which has then been drawn in the same manner as tubing towhich my adhesive-lamp black lubricants have The oil-lamp blackcompositions, however. did not permit satisfactory drawing of thetubing.

According to the provisions of the patent statutes, I have explainedtheprinciple and mode practicing my invention and have described what Inow consider to represent However, I desire to have it understood that,within the scope of the appended claims, the invention may be practicedotherwise than as speciilcally described.

I claim:

1. That method of cold working metal which comprises the steps ofproviding the metal with a solutions and its best embodiment.

coating ot-a mixture comprising lamp black and thus coated.

2. That method of colddrawing metal which.

3. That method of cold drawing metal which comprises the steps ofcoating the metal with a mixture comprising lamp black; lithopone, and aliquid adhesive, drying the coating on the metal, and cold drawing themetal while thus coated. I 4. That method of cold drawing ferrous metaltubing which comprises the steps of cleaning the tubing, providing itswith a coating of a mixture comprising lamp black and a liquid adhesive,and cold drawin the tubing while thus coated.

5. That method of cold drawing ferrous metal tubing which comprises thethe surfaces of the tubing prising lamp black and an aqueous sodiumsilicate' solution, drying the coating, and cold drawing the tubingwhile thus coated.

6. That method 01 cold drawing tubing which comprises the'steps ofcleaning the tubing, providing the surfaces with a coating of a mixturecomprising lamp black, lithopone, and an adhesive, and cold drawing thetubing while thus coated.

'7. A lubricant for cold drawing ferrous tubing comprising a mixture oflamp blackand a sodium silicate solution.

8. A lubricant for cold with a mixture comdrawing ferrous metal outerand inner surfaces steps of providing ferrous metal tubing comprising amixture of lamp black, lithopone, and an adhesive. I

HARRY K. IHRIG.

CERTlFI-QAIE OF CORRECTION.

Patent No. 2,067 ,530.

January- 12, 193" HARRY H. IHRIG.

It 'is hereby certified that error appears in the printed specifica ion0 the above numbered patent requiring correction as follows: Page 3,second column, line 1, claim 1, after the word "and" insert sodiumSilicate, and

1 cold working the metal while; and that the said Letters Patent shouldbe 5 read with this correction therein that the same may conform to therecord of the case in the Patent Office.

Signed and sealed this 9th day of March, A. D. 1937.

Henry Nan Arsdale (Seal) Acting Commissioner of Patents.

